The invention relates to method and apparatus for re-enforcing rotationally molded elements, particularly useful for thickwall products made of foamed plastics materials.
In the design of rotationally molded products it occasionally happens that certain parts are subjected to stresses higher than others; or that certain parts are inherently of less rigidity and/or strength due to their design, e.g. large-span planar portions.
One way of overcoming this difficulty is to increase the wall thickness of the product. This however, is a costly solution since, as known in the art of rotational molding it is very difficult to form products of varying wall thickness, and normally all the walls would have to be of excessive thickness without serving any useful purpose.
Another way for strengthening or stiffening weak product portions is to make them profiled. This, however, would certainly increase the manufacturing costs of the molding forms.
Still another method, applicable only in certain instances, is to bridge-over a gap between parallel walls so as to form internal contact points or lines through which the two walls would support each other (see FIG. 1). Again, this had requires special modifications of the molds.